This bizarre but potentially beguiling concoction is "Nixon in China," a pseudo-historic quasi-satirical opera-in-progress by everybody's favorite romantic minimalist, John Adams. (Remember "Harmonielehre"?)

With two intermissions and glib explanatory remarks by the composer himself, "Nixon" ran--sometimes crept--for three and a half trying hours Friday night at the Herbst Theater.

At this so-called "concert preview," the audience in the 1,100-seat hall shrank dramatically as the evening rambled on. That need not suggest a lost cause, however. Things could be very different by the time "Nixon" receives its much-ballyhooed full-scale premiere at the new Wortham Theatre in Houston in October (with reprises to follow in Brooklyn, Washington and Amsterdam).

When finally staged, the opera will no doubt benefit from the theatrical imagination of Peter Sellars, the fashionable enfant terrible who happened to conceive the project in the first place. Mark Morris, another avant-gardish Wunderkind, will no doubt provide off-the-Great-Wall choreography, including a heart-rending ballet divertissement inspired by "The Red Detachment of Women."

By October, the opera should be adorned with bona-fide orchestral accompaniment. The singers, for better or worse, will be outfitted with body mikes.

It all will be terribly daring, terribly mod, terribly chic, terribly up-to-date. It also may be provocative. It may even be fun.

The embryonic San Francisco version, sponsored by American Inroads in lieu of the defunct San Francisco Concert Opera, was just a sketchy token. The singers stood around and read the score from music stands. There were no sets, no costumes. There was no action.

The accompaniment was reduced--if that is the right verb--to two pianos and a synthesizer.

It is possible, though unlikely, that Adams will make major changes in his magnum opus before the autumn. Even if he does, he won't change his basic language, which is predicated on lush push-button sonorities, pretty second-hand effects, repetitive twaddle, rhythmic hyper-monotony and primitive piffle.

If one listens to the music without the advantage of dramatic distractions, it is possible to find sporadic passages that are genuinely engaging. Unfortunately, these passages are mired in somnolent sequential rituals that give ostinatos and arpeggios bad names.

Adams can crank out amusing movie-music bilge for satirical effect when he wants to. He obviously enjoys having his way with the mock-melodramatic gesture. He can burlesque operatic convention as well as the next fellow, and he does manage to use nice Sprechgesang explorations as counterpoint for his doodledy-doodledy instrumental meanderings.

If only it weren't all so simplistic.

Compounding the inherent stylistic problems, Adams has chosen to tread a precarious line between caricature and pathos. Ultimately, he falters. And falters. And falters.

Alice Goodman's libretto is often elegant and sometimes eloquent. As such it poses the threat of contextual shock.

The performance, stoically conducted by John DeMain , enlisted a stalwart little local chorus and most of the cast that will sing the Houston premiere.

Ronald Gerard, the modest, low-toned Kissinger, is not scheduled to repeat his relatively thankless assignment deep in the heart of Texas. A new singing statesman already has, no doubt, been cast. Under the circumstances, one left this complex and lofty endeavor haunted by only one profound question.